Removing the outer skin from bark containing fibres



May 1953 P. H. JOHNSON 2,835,928

REMOVING THE OUTER SKIN FROM BARK CONTAINING FIBRES Filed Oct. 51, 1955WEN inventor United States Patent Ofiice 2,835,928 Patented May 27, 1958REMOVING THE OUTER SKIN FROM BARK CONTAINING FIBRES Philip HenryJohnson, Hounslow, England, assignor to The Sudan Gezira Board, Barakat,Sudan, a Sudanese body corporate Application October 31, 1955, SerialNo. 543,775

3 Claims. (CI. 19-31) This invention relates to a process and apparatusfor removing the outer skin from bark which contains useful fibres.Certain barks, for instance the bark of cotton stalks, contain an innerlayer of useful fibres. The bark can be stripped from the stalks quiteeasily, but the bark itself is covered on the outside with a skin whichadheres tenaciously to the underlying layer of fibres. The removal ofthe outer skin is particularly desirable when the fibres are to besubjected to a chemical retting process, because if the skin is presentit adsorbs a substantial proportion of the chemicals used in the rettingprocess. Thus, removing the skin affords considerable savings in theretting process. However, the removal of the skin without harm to theunderlying layer of fibres has hitherto been difficult, and it is anobject of the present invention to provide an improved process, and anapparatus suitable for carrying out this process, for removing the skin.

According to one aspect of the present invention, a process for removingthe outer skin from bark containing fibres comprising drying the barkuntil the skin is in a brittle, crackable condition, subjecting the drybark to a crimping process as hereinafter defined for cracking the skininto small pieces, and removing these pieces from the underlying fibres.

By the term crimping is meant the application of pressure to limitedareas of the skin to such an extent that the skin is cracked in theseareas, the applied pressure being such as not to damage the underlyingfibres.

The crimping process may consist, for instance, of passing bark betweenrotating crimping rolls. Preferably the bark is passed successivelybetween crimping rolls in at least two different directions to producecrossing cracks in the skin. This can be done, for instance, by passingthe bark between the crimping rolls not only at right angles to the lineof the nip but also in at least one direction which is oblique to theline of the nip. This produces a criss-cross formation of cracks.

Many of the small pieces of skin between the cracks become detachedduring the crimping, while the remaining pieces can easily be removed byother methods such as become clogged, as might occur if solid flutedrolls were used.

Preferably the rolls are geared together to rotate in oppositedirections and so that the bars of one roll re main in the samerelationship to the bars of the other roll.

It is desirable that the distance apart of the rolls should beadjustable so that the degree of crimping effect given to the bark canbe adjusted to the point at which, though the skin is cracked, theunderlying fibres remain undam aged.

One form of apparatus embodying the invention will now be described byway of example with reference to the accompanying drawings in which:

Figure 1 is a side view of the apparatus partly in section; and

Figure 2 is a sectional plan view of the apparatus.

in the apparatus shown in the drawing two crimping rolls 10 and 11 aremounted in bearings 12 and 13 respectively on a frame 14 with theirshafts 15 and 16 parallel, the positions of the bearings 13 beingadjustable on the frame by means of adjusting screws 17 for the purposeof permitting adjustment of the distance between the rolls. The shaftshave flats 18 on one end so that either of the shafts can receive adriving handle or a coupling for a mechanical drive. The rolls aregeared together, through gearing comprising spur gears 19 and 20,sprockets 21 and 22 and a chain 23, so that they rotate at the samespeed in opposite directions.

Each roll is of squirrel-case form and consists of two end discs 24 and25 mounted on the shaft 15 or 16 as the case may be, between whichextend parallel bars consisting of stretched wires 26 each provided witha screw tensioning device 27. In addition to the individual tensioningdevices 27 all the wires of each roll can be adjusted collectively byproviding a threaded tensioning sleeve 28 which when rotated relativelyto the shaft adjusts the axial position of the disc 24 on the shaft, thesleeve 28 being constrained against axial movement on the shaft. Ifsufliciently taut, wires 26 of up to about a foot in length can be usedwithout intermediate support. If longer rolls are required, intermediatesupporting discs (not shown) may be provided.

In stead of bars consisting of tensioned wires 26, untensioned bars of across-section which provides suflicient rigidity may be provided.

In using the apparatus, dried bark is passed between the rotatingcrimping rolls 10 and 11 and the distance between them is adjusted bymeans of the screws 17 until the skin is effectively cracked but theunderlying fibres are not harmed. When the correct adjustment has beenachieved, dried bark can be passed between the rolls continuously,preferably at least three passes being made, either between the samepair of rolls or between different pairs of rolls. One pass may be atright angles to the line of the nip while the other passes may beoblique to this line in opposite directions, so as to produce acriss-cross formation of cracks on the bark. The bulk of the smallpieces between these cracks will come away during the crimping, but anysmall pieces that may still remain can be removed by one of the methodsmentioned above.

What I claim as my invention and desire to secure by Letters Patent is:

1. Crimping apparatus for producing cracks in the ski'nof dried bark inwhich said skin is in a brittle crackable condition, comprising twocrimping rolls disposed with their axes parallel and means for rotatingsaid rolls in opposite directions, said rolls each comprising two spacedend discs, wires extending between said end discs parallel with the axisof said roll and spaced from one another and means for maintaining thesaid wires in tension.

2. Crimping apparatus according to claim 1 in which each of said rollsinclude means for adjusting the distance between the end discs thereof.

3. Crimping apparatus according to claim 1 in which each of said wiresis provided with an individual tensioning device. a

References Cited in the file of this patent 8 UNITED STATES PATENTSWheaton Mar. 7, 1882 McBride Sept. 16, 1890 Schlichten Mar. 26, 1912Lacroix Oct. 25, 1913 Colahan Aug. 12, 1915- Burkardt Nov. 19, 1937FOREIGN PATENTS Great Britain Sept. 29, 1857 Great Britain Feb. 7, 1929Great Britain Oct. 28, 1940

